feature request: merge annotations into pdf popup annotations

[jurgenvinju]

Loving this project!

It would be great if we could use pdf.js's annotation features to map hypothesis annotations to PDF annotations.

• This would be good (for example) just before a print, such that the PDF printer driver can make something nice out of the annotations.
• Another usecase is to share annotated PDFs via interfaces that expect annotated PDFs (journals and other types of editing environments).

Outline of the feature which would be a part of the "print" button, or an extra "export" button:

• maps normal annotations to pdf popup annotations
  • optionally include group name and/or author name (good for anonymous reviews)
  • requires a pop-up with options or pre-configured setting somewhere else
• maps page annotations to marging notes? free text. don't know what the best thing to do is
  • same optional mentioning of group/author name
• maps highlights to highlights
• If author names are not to be included in the annotations, then this feature should guarantee the privacy of the authors of the annotations. no meta-data should be included in the PDF that could reveal their identity.

[robertknight]

Related general issue - https://github.com/hypothesis/product-backlog/issues/566. I'll keep this one open since it's much more specific.